Process for pyrolitic decomposition of hydrocarbons



M. B. cooKE 2,016,798

PROCESS FOR PYROLYTIC DECOMPOSITION OF HYDROCARBONS Oct. 8, 1935.

Filed March l2, 1932 c k R. 0 m w w N m w w m T W A w M LJ GSW Qxv BPatented Oct. 8, 1935 UNITED s'm'rizs PATENT OFFICE PRooEss FonrYRoLrrro DEooMrosrrloN oF rrrnnooamsoivs My invention relates to aprocess for the'pyrolytic decomposition of hydrocarbons to formgasoline-like hydrocarbons suitable for using las a motor fuel havinghigh antiknock qualities. The

process' is usually known as a cracking process and relates moreparticularly tothe cracking of hydrocarbons in the vapor phase by hotgases of combustion.

When fuel is burned with no excessive air, the

10. temperature of combustion is between 3,000 and 4,000 F. Thesetemperatures are too high for efficient cracking and accordingly theymust be tempered or brought down to about 1500 F. in order to give anefficient cracking process.

15 In an lapplication of William O. Keeling, Serial No. 586,573, now U.S. Patent 1,991,750, a method of tempering the combustion gases by meansof a cooler, inert gas is disclosed.

This application relates to a process in which 20 the combustion gasesare tempered in a novel and more eiiicient manner.

When a great volume of gas is introduced into the fractionating tower,many disadvantages result. 'The equipment must be lmade of a larger 25size. The volume of gas to'be compressed for absorption purposes is soincreased that the process becomes expensive. The use of a cool, inertgas to temper the combustion gases represents a direct loss of heatbesides increasing the volume 30 of the gases to be handled.

. One object of my invention is to avoid the disadvantages above pointedout.

Another object of my invention `is to provide a. process in which thehot gases of combustion 35 are tempered by means of heat exchange.

A further object 'of `my invention is to employ the gas heat for toppingthe charging stock, vaporizing the charging stock for conversion intothe vapor phase and supplying heat for other 40 purposes such asdistilling the rich absorption oil which contains gasoline or thegeneration or high superheatlng of steam.

Still another object of my invention is to provide a vapor phasecracking process in which hot 45 gases of combustion are used to supplythe cracking heat which is iiexible of control and efficient inoperation. a

Still another object of my invention is to check the reaction to preventover-cracking by means 50' oi shock chilling the products of reaction.

Other objects of my invention will appear from the followingdescription: i

'I'he gure shows a diagrammatic view of one embodiment of the process ofmy invention.

In general, my invention consists in burning fuel and air with surfacecombustion in a furnace to supply hot gases of combustion substantiallydevoid of free oxygen. I charge crude oil from storage through suitableheat exchangers through a coil situated within the furnace. Thetemperature of the hot gases of combustion will be lowered and lose partof their heat in heating the incoming charge during its passage throughthe topping heating coil. The heated products are discharged into afractionating tower preferably of the bubble type, whence the vapors arewithdrawn overhead, condensed and passed intoy a separator. The gasolineis withdrawn from the separator and passed to storage. A fractioncollects in the separator and is reiiuxed into the bubble tower. Thereiiux condensate from the bubble tower may be pumped to storage andforms in part the cracking stock which is used in my process. The reuxcondensate may, if desired, be pumped directly-through suitable heatexchangers into an Vaccumulator tank.' Oil is pumped from theaccumulator tank through suitable heat exchangers, through a second coilsituated` in my'furnace where the heat necessary to convert asubstantial portion ofthe charging -stock into vapors is supplied. Theheated charging stock is passed into a fiash evaporator whence thevapors are withdrawn and passed 'to the cracking zone. In the crackingzone the vaporized hydrocarbons encounter the hot gases of combustionwhich have been tempered to about 1500 F. The hot gasesvof combustionadmixing with the vapors bring the mixture to about41050 F. at whichtemperature lcracking ytakes, place rapidly. 'I'he increasel inlvolumeis accommo- 35 dated for by a progressively increasing cross sectionalarea. After leavingvthe vcracking zone, the products of; the reactionare shock chilled by means of an oil spray. The products, after beingchilled, pass into a tar separator. The tar laden quenching oil isldrawn through a cooler and pumped to storage and may be used for fueloil. The vapors andgases vare passed through a sectional entrainmentcondenser and then into a fractionating tower. The condensate fromtheentrainment condenser collects in suitable pockets y and may be passedeither into the separator or into a fractionatingtower dependingupontheir nature and character. 1 A

The reilux condensate from the fractionating tower is withdrawn andpumped through acooler in order to reduce the temperature thereof torender it suitable as a quenching medium. vAfter `passing through thecooler, it is passed through the sprays in order to be used in thechilling zone. f

' A portion of the reflux condensate of the fracy oil in a gasolineabsorption process.

A fat oil drawn from the bottom of the absorber is passed into a steamstill to recover a gasoline fraction. The fixed gas is passed into a gasmain to supply fuel for the burner of the furnace.

More particularly referring now to the drawing, the crude oil fromstorage is charged through line I and pumped by pump v2 through heatexchanger 3, Ithrough heat exchanger 4, through topping heating coil 5,where the crude oil being charged is heated. The-heat imparted to theincoming crude lowers the temperature of the combustion gases. The oilleaves the topping heating coil through line 6 and is charged into thefractionatingltower 1. 'This tower is preferably of the bubble type butit is to be understood that any suitable fractlonating column may beemployed. The topped oil is withdrawn through line 8 and pumped by pump9 through heat exchanger 4. If valve I8 be closed, and valve I I beopened, the oil will pass through cooler I2 into storage I3. The coolerI2 is cooled by circulating water or any suitable means. The pump I4will pump oil from the cracking stock storage tank I3 if valve I5 beopen. If valves I5 and II be closed and valve I0 open, the topped crudewill pass through line I6 into line I1 to pump I4.

`The vapors from the bubble tower 1 are withdrawn through line I8,through heat exchanger 3 into cooler I9 where they are condensed. 'Ihecondensate passes through line 28 into separator 2l. The gasoline iswithdrawn through line 22 and passed to storage. A fraction is withdrawnfrom the separator throughline 23 by pump 24 and pumped back into thebubble tower 1 as a reflux. The topped crude is pumped by pump I4through heat exchanger 25, through heat exchanger 26, through heatexchanger 21, whence it passes through'line 28 into the accumulator 29.The charging stock thus preheated is withdrawn through line SI!l by pump3| and is pumped through line 32, it being understood that valves 33 and34 are open and valve 35 is closed. The charge passes from line 32through the tubing 36 of the sectional entrainment condenser 31 andleaves said condenser through line 38 passing through valve 34 into line39, through theI vaporizing heating coil 40. The products of combustionin the furnace are tempered by losing some of their heat to the chargingstock passing through coil 40. The heated charging stock leaves the coil48 through line 4I and passes into the flash evaporator 42. 'I'heunvaporized oil from the flash evaporator may pass through line 43.through valve44, through line 4 5, into the accumulator 29. Line extendsfrom the accumulator 29 to the flash evaporator 42 and serves as a vaporrelease line permitting any vapors in the accumulator to escape into theflash evaporator. If desired, valve 44 may be closed and valve 46 may beopen so that the unvaporized oil will pass through line 41 into .line 48through cooler 49, where it is pumped by pump 50 to storage as fuel oil.The vapors from the ila-Sh evaporator will pass through line 5I and bedischarged into a mixing zone 52. Valve 5I' controls the vapor flow.

Gas is withdrawn from the gas main 53 through branch line 54 andcompressed by compressor 55 into gas supply tank 56, whence gas iswithdrawn through line 51 being controlled by valve 58 into the mixingchamber 59' of a surface combustion burner. Compressed air, controlledby valve 6I', also passes into the mixing chamber 59'. The

mixture burns with surface combustion about the refractory granules 62of the surface combustion burner 63. The hot gases of combustion willpass into the furnace 64 and be tempered by heat exchange with thematerial passing through coils 40 and 5 respectively and into the mixingzone 52, whence a commingling of the hot products of combustion sotemperedy to about 1500 F. will take place with the hydrocarbon vaporscoming from the flash evaporator 42. After admixture, the temperaturewill be about 1050 F. and cracking or pyrolitic decomposition will takeplace rapidly.

As cracking takes place, the volume of the products will increase and,in order'to prevent the building up of pressure, a progressivelyincreasing cross-sectional volume of the cracking chamber is provided.

Inasmuch as the cracking will take place very rapidly, at thetemperature of 1050 F., I resort to shock chilling or cracking chamberof quenching to reduce the temperature of the products of reaction from1050 to '700 F. l I do this by means of oil sprays 53', 54', 55,`and56', oil spray 56 being located in the tar separator 51. The temperatureof '700 is low enough to prevent any further reaction and high enough topermit the distillate to escape in the vapor state into thefractionating tower. The heavy, tarry fuel oil, however, will accumulatein the bottoms of the separator 51. 'I'his tar laden quenching oil iswithdrawn through line 58 which joins with line 41 and permits the fueloil bottoms to be passed through the cooler 49 to fuel oil storage.

The vapors from the tar separator 51 pass overhead through line 59 intoa sectional entrainment condenser 31, whence they will pass incounterflow relation to the incoming charging stock which is passingthrough tubes 36. The hot vapors will be cooled considerably by theincoming charging stock which in turn will be heated. The condensate isallowed to collect in compartments 60, 6I and 62. The condensate may bewithdrawn from the respective compartments and selectively passed intothe separator or fractionating tower through lines 63 and 64respectively. The condensate may be supplied as desired by means ofvalves 65, 66, 61 and 68, so that all or part of the condensatecollected in the sectional entrainment condenser 31 may be passed toeither the separator or the fractionating tower as desired and dependingupon the nature of the condensate. The vapors and gases leave thesectional entrainment condenser through line 69 and pass into thefractionating tower 10. The reflux condensate from the fractionatingtower is withdrawn through line 1I and passed through heat exchanger 21,through line 12, through pump 13, through cooler 14 and through line 15into line 16, which terminates in a manifold for the quenching sprays.The quenching oil leaves line 15 through valve controlled lines 11, 18,19, and 80. If desired, a portion of the reflux condensate from thefraction ating tower may be diverted through valve conthe superheatedsteam will be condensed in cooler- 83 and will form water in the bottomof the separator 85. This water is withdrawn through line 88. Thegasoline-like hydrocarbons are withdrawn through line 81 and passed tostorage. The gases from' the yseparator will contain a quantity of gasrich in gasoline-like hydrocarbons. Accordingly, I propose to withdrawit,

through line 88 and compress thegas in compressor 89, pass it throughcooler 90 into receiver 9|. The cooling and compressing will precipitatefurther gasoline-like hydrocarbons which are withdrawn through line 92and pass into line 81 to storage. 'Ihe gases from the receiver arewithdrawn through line 93 and passed into the gasoline absorption tower94 where it is scrubbed by lean oil entering through line 95. The fixedgas is withdrawn through line 96 into gas main 53. The fat oil from thebottom of the absorption tower BI-is withdrawn through line 91 andpassed to a steam still for the distillation therefrom of thegasoline-like hydrocarbons.

It will be appreciated that my process has many advantages. I temper thehot products of combustion by means of heat exchange and use the heatobtained by tempering to perform useful steps in my process. 'Ihethermal efficiency of my process will be exceedingly high. Theilexibility of control is manifest. The temperature of the combustiongases, the temperature of the quenching loil and hence the temperatureof reaction may be controlled within close limits. I am enabled by myprocess to crack hydrocarbon oil in the vapor phase and obtain agasoline-like hydrocarbon suitable for use 'as a motor fuel and havingan exceedingly high antiknock value. I may use a portion of the gasformed in my process for otherv purposes where gaseous fuel maybeneeded. It.wi11 be noted that the cracking reaction takes place in thepure vapor phase, it being impossible for any hydrocarbon oil which isnot in the vapor form to be present. This insures the absence of thedanger of the formation of coke or carbon deposits within my crackingzone. It will be understood, of course, that suitablel lagging isprovided throughout the piping and the piece of apparatus used in myprocess to prevent the loss of heat by radiation.

It will be understood that certain features, subcombinations andoperations are of utility and may be employedwithout reference to otherfeatures and sub-combinations. This is contemplated by and is within thescope of my claims. It is further obvious that various changes may bemade in details within the scope of my claims without departing from thespirit of my invention. It is, therefore, to be understood that myinvention is not tobe limited to the specific details shown anddescribed. s

By this method of cracking hydrocarbons in the vaporphase, in which thehydrocarbons arey combined with the combustion gases, the latter beingmaintained at selected, controlled temperatures of reaction, a motorfuel having a high octane number and high antikneck value is obtained.The process eliminates parasitic cracking which accompanies conventionalcracking y drocarbons to take place to`form gasoline-like methods, inwhich the hydrocarbons are converted in tubular containers and heatedbyexternal circulation of the combustion gases thereabout. The intimatemixture of the combustion gases with the hydrocarbonfvapor produces adistribution of heat impossible with the conventional tubular crackingprocesses.

Having Athus described my invention, what I claim is:

l. The process of converting hydrocarbon oil into gasoline-likehydrocarbons of lower molecular weight which includes the steps ofgenerating hot combustion gases, passing the hydrocarbon oil to becracked in indirect heat exchange with said hot combustion gases toreduce the temperature of the gases and effect a heating of the oilsubstantially without pyrolytic decomposition,

subjecting the hydrocarbon oil thus heated to a topping operation,passing the topped hydrocarbon oil in indirect heat exchange with said20 with said tempered products of combustion and permitting a pyrolyticdecomposition of said hyhydrocarbons having a lower molecular weight.v

2. The process of converting hydrocarbpn oil into gasoline-likehydrocarbons of lower molecular weight which includes the steps ofgenerating hot combustion gases, passing the hydrocarbon oil to becracked in indirect heat exchange with said hot combustion gases toreduce the temperature of the gases and effect a heating of the oilsubstantially without pyrolytic decomposition, subjecting the oil thusheated to a topping operation, passing the topped oil as thehydrocarbons to be cracked in indirect heat exchange with saidcombustion gases `to lower their temperature,

flashing the oil thus heated into vapors in a vapor- 40 izing stage,directly commingling said vapors with said tempered products'ofcombustion, permitting a pyrolytic decomposition of said hydrocarbons totake place to form gasoline-like hy` drocarbons having a lower molecularweight, and 45 stopping said reaction by spraying oil into the reactingmixture after the reaction has progressed a desired extent wherebyover-cracking is prevented.

3. The processl of into gasoline-like hydrocarbons' of lower molecularweight which includes the steps of generating hot combustion gases,passing the hydrocarbon oil to be cracked in indirect heat exchange withsaid hot combustion gases to reduce the temperature of the gases andeffect a heating of the oil substantially without pyrolyticdecomposition, subjecting the oil thus heated to a topping operation,passing the oil as the hydrocarbons to converting hydrocarbon oil 50 becracked in indirect heat exchange with said combustion gases to lowertheir temperature, flashing the oil thus heated into vapors in avaporizing stage, directly commingling said varpors with said temperedproducts of combustion',

permitting a pyrolitic decomposition of said hydrocarbons to take placeto form gasoline-like hydrocarbons having a lower molecular weight,fractionating the 'products of reaction, and withdrawing the refluxcondensate from the fractionating stage. l

4. The process of converting hydrocarbon oil into gasoline-likehydrocarbons of lower molecular weight which includes the steps ofgenerating hot combustion gases, passing the hydrocarbon oil in indirectheat exchange with said hot combustion gases to reduce the temperatureof the gases and effect a heating of the oii. substantially withoutpyroiytic decomposition, subjecting the oil thus heated to a. toppingoperation passing the topped oil as the hydrocarbons to be cracked inindirect heat exchange with said combustion gases to lower thetemperature thereofi flashing the oil thus head into vapors in avaporizing stage, directly commn'gling saidyapors with said 10 temperedproducts of combustion, permitting apymlyizic decomposition oi' saidvapors to take -place'to form gasoline-like hydrocarbons having a lowermolecular weight, fractionating the products of the reaction,withdrawing the vapors and gases from the fractionating stage, coolingsaid vapors and gases, withdrawing-the condensate formed in the coolingstage,l and subjecting the uncondensed gases to gasoline absorptiontreatfment.

MAURICE B. COOKE.

